1 files changed, 91 insertions, 0 deletions
diff --git a/substdi.c b/substdi.c
new file mode 100644
index 0000000..42407a1
--- /dev/null
+++ b/substdi.c
@@ -0,0 +1,91 @@
+#include "substdio.h"
+#include "byte.h"
+#include "error.h"
+
+static int oneread(op,fd,buf,len)
+register int (*op)();
+register int fd;
+register char *buf;
+register int len;
+{
+  register int r;
+
+  for (;;) {
+    r = op(fd,buf,len);
+    if (r == -1) if (errno == error_intr) continue;
+    return r;
+  }
+}
+
+static int getthis(s,buf,len)
+register substdio *s;
+register char *buf;
+register int len;
+{
+  register int r;
+  register int q;
+ 
+  r = s->p;
+  q = r - len;
+  if (q > 0) { r = len; s->p = q; } else s->p = 0;
+  byte_copy(buf,r,s->x + s->n);
+  s->n += r;
+  return r;
+}
+
+int substdio_feed(s)
+register substdio *s;
+{
+  register int r;
+  register int q;
+
+  if (s->p) return s->p;
+  q = s->n;
+  r = oneread(s->op,s->fd,s->x,q);
+  if (r <= 0) return r;
+  s->p = r;
+  q -= r;
+  s->n = q;
+  if (q > 0) /* damn, gotta shift */ byte_copyr(s->x + q,r,s->x);
+  return r;
+}
+
+int substdio_bget(s,buf,len)
+register substdio *s;
+register char *buf;
+register int len;
+{
+  register int r;
+ 
+  if (s->p > 0) return getthis(s,buf,len);
+  r = s->n; if (r <= len) return oneread(s->op,s->fd,buf,r);
+  r = substdio_feed(s); if (r <= 0) return r;
+  return getthis(s,buf,len);
+}
+
+int substdio_get(s,buf,len)
+register substdio *s;
+register char *buf;
+register int len;
+{
+  register int r;
+ 
+  if (s->p > 0) return getthis(s,buf,len);
+  if (s->n <= len) return oneread(s->op,s->fd,buf,len);
+  r = substdio_feed(s); if (r <= 0) return r;
+  return getthis(s,buf,len);
+}
+
+char *substdio_peek(s)
+register substdio *s;
+{
+  return s->x + s->n;
+}
+
+void substdio_seek(s,len)
+register substdio *s;
+register int len;
+{
+  s->n += len;
+  s->p -= len;
+}